CASE SELECTION; AND
SAMPLING
Susan Kilonzo
Case studies
• A case could be anything (event, process, activity, actors…).
• However, a case can analytically be separated from its
environment.
• It is therefore a spatially bounded phenomenon observable at a
given time.
• Case Study is an intensive analysis (qual or quant) of a single
unit (case) or a small number of units (cases)
• A detailed analysis of the relationships between the
contextual factors and an natural occurrence e.g. (GBV and
natural disasters?)
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What is a case?
• A case could be anything (event, process, activity,
actors…).
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Determining a Case in a Hospital
Study- Several units
In defining your case…
• Determine :
• What do I study? – region, an individual, an organisation, a
process, a system, activity?
• What are your decision points in defining cases (analytic
gains and losses of these boundaries)- Success story of Botswana
• Determine what the case is not Bounding:
• A case has two boundaries which are to be well defined:
space and time
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Determining a Case
• The research question determines cases we select.
• Example 1: How has Devolution Influenced Access to Referral
Maternal Healthcare in Western Kenya? (Kilonzo et. al)
• Perceptions from users and providers
• Example 2: How has devolution improved access to
referral maternal healthcare in Kisumu and Uasin
Gishu Counties in Kenya? Kilonzo et. al.
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More examples
• How does land consolidation affect agricultural production
in Amhara and Afar regions of Ethiopia?
• How does local leadership influence different election
outcomes in Nigeria?
• To what extent do the interventions on FGMs vary across
different regions in Northern Sudan?
• How has the implementation of free day secondary
education improved student retention in Kenya?
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Determining a Case
• Consider your decision points in defining
cases
• Ask yourself:
• do I want to “analyze” the individual?
• Do I want to “analyze” a program?
• Do I want to “analyze” the process?
• Do I want to “analyze” the difference between
organizations?
• In comparative cases, ask yourself, what is
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Separating/Bounding a case
• Once you determine what your case is, also
consider what it is NOT.
• A case can analytically be separated
(bounded) from its environment.
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Strategies for bounding a case:
• Time and space:
How has Devolution (introduced in 2013) in the health sector
Improved Access to Referral Maternal Healthcare in Kisumu and
Uasin Gishu Counties?
• Time and activity:
How has devolution improved access to referral maternal
healthcare for women working in the informal sector?
• Time, definition and context
How has devolution improved access to referral maternal healthcare for
middle class women in rural areas?
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Selecting cases
• Considerations…
• Purpose for which cases are selected/goal of researcher
(causality; causal mechanism, description, exploration,
comparison).
• Availability of data
But why not choose cases randomly to avoid biases?
Case Selection (Gerring, 2007)
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Determining how to do a case
study
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Determining paths in case studies
• Individual case (interest is details of one case, not to
compare across cases)
• Comparative (differences and similarities)
• Causality (causal chain/mechanism).
Sampling
What is Study Population? sampling? Sample?
• The word ‘population’ is used to describe the target group.
• A sample is a section of units from the wider population
which will be engaged in the study.
• Sampling is the process of identifying who you will aim to
contact from that population.
• A sampling frame is a list of members of a population from
which members of a sample are then selected.
Sampling Techniques
• Sampling is categorised into three:
• Probability sampling
• Non-probability sampling
• Mixed Method Sampling
Probability Sampling
Probability sampling allows all the elements of the target
population stand a chance of being selected into the study
sample.
These are primarily used in quantitatively oriented studies and
involve ‘‘selecting a relatively large number of units from a
population.
Types:
• Random sampling (ballot & systematic)
• Stratified Sampling
• Cluster sampling
• Multi-stage sampling (sampling across hierarchical levels)
Non-Probability
This is sometimes called purposive sampling.
Types of Purposive Sampling
• Sampling to Achieve Representativeness or Comparability
• Sampling Special or Unique Cases
• Sequential Sampling
• Sampling Using Multiple Purposive Techniques
Types of Convenience Sampling (Non-probability)
• Captive Sample
• Volunteer Sample
Mixed-Method Sampling Procedures
Basic Mixed Methods Sampling
• Sequential Mixed Methods Sampling
• Concurrent Mixed Methods Sampling
• Multilevel Mixed Methods Sampling
• Combination of Mixed Methods Sampling Strategies